[Lldb-commits] [PATCH] D83359: [SymbolFileDWARF] Lock the module when parsing call site info

[Vedant Kumar via Phabricator via lldb-commits]

vsk updated this revision to Diff 276280.
vsk added a comment.

Move locking up into lldb::Function, and leave a comment in SymbolFileDWARF explaining why.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83359/new/

https://reviews.llvm.org/D83359

Files:
  lldb/include/lldb/Symbol/Function.h
  lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
  lldb/source/Symbol/Function.cpp


Index: lldb/source/Symbol/Function.cpp
===================================================================
--- lldb/source/Symbol/Function.cpp
+++ lldb/source/Symbol/Function.cpp
@@ -290,6 +290,8 @@
 }
 
 llvm::ArrayRef<std::unique_ptr<CallEdge>> Function::GetCallEdges() {
+  std::lock_guard<std::mutex> guard(m_call_edges_lock);
+
   if (m_call_edges_resolved)
     return m_call_edges;
 
Index: lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -3844,6 +3844,11 @@
 
 std::vector<std::unique_ptr<lldb_private::CallEdge>>
 SymbolFileDWARF::ParseCallEdgesInFunction(UserID func_id) {
+  // ParseCallEdgesInFunction must be called at the behest of an exclusively
+  // locked lldb::Function instance. Storage for parsed call edges is owned by
+  // the lldb::Function instance: locking at the SymbolFile level would be too
+  // late, because the act of storing results from ParseCallEdgesInFunction
+  // would be racy.
   DWARFDIE func_die = GetDIE(func_id.GetID());
   if (func_die.IsValid())
     return CollectCallEdges(GetObjectFile()->GetModule(), func_die);
Index: lldb/include/lldb/Symbol/Function.h
===================================================================
--- lldb/include/lldb/Symbol/Function.h
+++ lldb/include/lldb/Symbol/Function.h
@@ -17,6 +17,8 @@
 #include "lldb/Utility/UserID.h"
 #include "llvm/ADT/ArrayRef.h"
 
+#include <mutex>
+
 namespace lldb_private {
 
 class ExecutionContext;
@@ -655,6 +657,9 @@
   uint32_t
       m_prologue_byte_size; ///< Compute the prologue size once and cache it
 
+  std::mutex
+      m_call_edges_lock; ///< Exclusive lock that controls read/write
+                         ///  access to m_call_edges and m_call_edges_resolved.
   bool m_call_edges_resolved = false; ///< Whether call site info has been
                                       ///  parsed.
   std::vector<std::unique_ptr<CallEdge>> m_call_edges; ///< Outgoing call edges.


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